In recent years, medical implants have made profound changes in medicine. When implanted within various parts of the human body, these devices perform important in vivo functions including diagnosis, monitoring, and disease treatment. It is clear that the line between biology and technology is blurring, and biological tissues and man-made machines are becoming integrated. This trend will have a broad impact on the future practice of medicine.
Although many technical barriers for designing and utilizing implantable devices have been removed, there still exist two significant problems: (1) they require an electrical energy supply, and (2) they often require a data communication link. Since existing designs, some of which are described below, have many drawbacks, these problems are hampering the development of the next-generation implants.
Currently, most implantable devices within the body, such as cardiac pacemakers and deep brain stimulation devices, use non-rechargeable batteries as power supplies. Because the batteries inside an implantable device cannot be replaced easily without surgery, different approaches have been studied to power implantable devices by delivering electrical energy transcutaneously from outside of the human body. In some cases, wire connections across the skin have been utilized. Clearly, this percutaneous design is highly invasive and prone to infection. Various designs using, for example, magnetic inductive coupling, ultrasound, optical coupling, and volume conduction have been reported. In most of these designs, an energy transmitter is carried or worn by the patient. This transmitter couples with an energy receiver inside the body to transmit electrical energy. Although these designs provide power supplies for implantable devices in principle, the external device with cables carried or worn by the patient is often cumbersome and inconvenient in the daily life of patients. Thus, there is a need for a portable, preferably low-cost, and convenient apparatus that may be used as a platform to supply electrical power to and communicate with implantable devices.